A touch panel capable of providing an intuitive user interface (UI) for the user is widely used as a device for accepting input operation to an electronic apparatus including a portable phone or a smart phone, for example. The touch panel accepts input operation to the screen of a display unit (for example, an LCD (liquid crystal display) or an organic EL (electroluminescence) display) provided for such an electronic apparatus, and the results of the processing for the input operation are displayed on the screen.
In addition, recently, a touch panel capable of detecting the proximity of a finger is known (for example, refer to Patent Document 1). The non-contact-type user input device of Patent Document 1 includes a plurality of linear transmission electrodes, a transmitter for supplying an AC current for transmission to the respective transmission electrodes, a plurality of linear reception electrodes disposed so as not to make contact with the respective transmission electrodes, and a receiver for receiving the AC current flowing through the reception electrodes. A capacitor is formed at each intersection of the transmission electrode and the reception electrode. Furthermore, since a capacitor is formed in response to the proximity of the fingertip of the user, the electrostatic capacitance value of the capacitor changes depending on the degree of the proximity of the fingertip. The non-contact-type user input device can recognize the distance between the touch panel and the finger on the basis of the change in the electrostatic capacitance value.
The touch panel of Patent Document 1 can detect a state in which the finger is held over at a position in the space at a predetermined height or less from the horizontal plane of the touch panel, that is, the proximity state of the finger with respect to the touch panel, whereby on the basis of the electrostatic capacitance value determined by the distance between the finger and the touch panel, the touch panel can detect that the finger in the space was slid in nearly parallel with the touch panel as in the case that the finger directly touched the touch panel and was slid on the touch panel. Hence, it is expected that such a touch panel capable of detecting the proximity of the finger will be accepted comprehensively as a new user interface.
Moreover, a keyboard device is known in which a touch panel detects the position of a finger making contact with a screen on which the content (key tops) of the keyboard is displayed and a finger sensor unit detects the position of the finger proximate to the screen (for example, refer to Patent Document 2). In the keyboard device of Patent Document 2, only the key frames of the keys proximate to the position of the finger detected by the finger sensor unit are magnified and displayed and the key frames of the keys away from the position of the finger are reduced and displayed. The finger sensor unit of Patent Document 2 is configured using an optical sensor or an infrared sensor.